For example: I want to display my product’s image in 3 different sizes in quick view, shopping cart, frontend store and magnified part (something like amazom.com). For this purpose, should I add four different images in different sizes or can I add just one image in large size and make other 3 sizes by customizing magento source code?
By Default Magento provides, amazon-like functionality.
You can set your image like thumb, base, small image.
For Thumbnail image, They will display at Product page Gallery thumbnail, Shopping cart page.
For Small Image will Used in Related, Upsell and cross sell section of site.
For Base image used in product page main image.
So you need to setup all the images from admin panel catalog -> product with all of the within single image.